1. Field of the Invention
The present invention is related to a programmable gain amplifier, and more specifically to a programmable gain amplifier used in an IF demodulator.
2. Related Art
Programmable gain amplifiers (PGAs) are used in various analog signal processing applications where an electrical signal of varying amplitude must be either amplified or attenuated before subsequent signal processing.
Various gain and/or attenuation settings are required to accommodate the wide dynamic range needed for the amplifier's input stages.
In a typical automatic gain control (AGC) system, a PGA should be monotonic in order to maintain stability for the AGC loop, or simply to ensure the control circuit functions properly.
In an IF demodulator or TV system, a programmable gain amplifier needs to have a large bandwidth to accommodate the high frequency nature of the input signal. An amplifier also needs to have a high signal-to-noise ratio and high linearity to maintain picture quality. Further, an amplifier is needed that will maintain a large gain range with a very small step size.